This invention relates to heat curable silicones having improved room temperature stability. More specifically, this invention deals with silicone compositions that are curable at elevated temperatures by the catalyzed reaction of silane, hereinafter also SiH, groups to silicon-bonded vinyl groups, hereinafter also SiVi, and/or silicon-bonded hydroxyl groups, hereinafter also SiOH.
The reaction of SiH groups with SiVi and/or SiOH groups is a well known reaction for crosslinking silicone resins, elastomers, and coatings.
While this reaction provides rapid cure at elevated temperatures, there is an unfortunate tendency for cure to proceed slowly at room temperature. This tendency limits the amount of time a composition can be stored before use, as well as the work life of a composition in an industrial process.
This problem has been dealt with in two general ways: separation of the reactants until just before use, and the use of inhibitors.
Separation of the reactants before use is generally accomplished by providing the heat curable composition in two parts. One of these parts contains the SiH containing component, while the other contains the SiVi and/or SiOH containing component, and the catalyst. These two parts are then mixed prior to use.
There are disadvantages to the use of such two part systems however. Among other disadvantages, expenses related to packaging, shipping, handling, and storage are increased.
In addition, in such applictions as release coatings, where very rapid cure is essential, high levels of reactive groups and catalyst are used. A release coating supplied in two parts must still maintain a reasonable stability, after the two parts are mixed, to be practical.
The use of inhibitors is another solution to the problem of lack of room temperature stability.
The patent literature, for example, discloses the following classes of compounds as inhibitors for the reaction of SiH groups with SiVi and/or SiOH groups:
vinyl amides PA1 hydroperoxides PA1 aminoalkyl silanes PA1 various metal salts PA1 sulfoxides PA1 acrylonitrile derivatives PA1 acetylene derivatives, such as PA1 dialkylacetylene dicarboxylates and PA1 ethynylically unsaturated isocyanurates, PA1 phosphines, PA1 phosphites, PA1 nitrogen-containing hydrocarbons, such as pyridine, PA1 dithiocarbamate derivatives, and the like. PA1 (A) a silicone containing SiVi groups and/or SiOH groups; PA1 (B) A silicone containing SiH groups; PA1 (C) a catalyst; PA1 (D) A conjugated ene-yne; and PA1 (E) vinylcyclosiloxanes. PA1 (A) a polyorganosiloxane having the general formula R.sub.3.sup.2 SiO(R.sup.1.sub.a Q.sub.b SiO.sub.(4-a-b)/2).sub.x SiR.sub.3.sup.2, wherein PA1 (B) a polyorganosiloxane containing hydrogen atoms bonded to silicon atoms; PA1 (C) a catalyst; PA1 (D) a conjugated ene-yne, said conjugated ene-yne characterized by having: PA1 (E) a vinylcyclosiloxane having the general formula EQU (R.sup.5 CH.sub.2 .dbd.CHSiO).sub.m PA1 HOMe.sub.2 SiO(MeViSiO).sub.5 (Me.sub.2 SiO).sub.95 SiMe.sub.2 OH; PA1 Me.sub.3 SiO(MeViSiO).sub.20 (Me.sub.2 SiO).sub.20 SiMe.sub.3 ; PA1 Me.sub.2 ViSiO(MeViSiO).sub.6 (Me.sub.2 SiO).sub.98 SiMe.sub.2 Vi; PA1 HOMe.sub.2 SiO(Me.sub.2 SiO).sub.4000 SiMe.sub.2 OH; PA1 a resin composed of Me.sub.2 ViSiO.sub.1/2 units, Me.sub.3 SiO.sub.1/2 units and SiO.sub.4/2 units; PA1 R.sup.3.sub.c H.sub.d SiO.sub.(4-c-d)/2, wherein PA1 R.sup.3 is a non-olefinic monovalent hydrocarbon or halogenated hydrocarbon radical as described for R' of component (A); PA1 H is a hydrogen atom; PA1 c has a value of 0, 1, 2 or 3; and PA1 d has a value of 0, 1, or 2; there being at least one unit wherein d has a value of 1. PA1 (MeHSiO).sub.5 ; PA1 Me.sub.2 HSiO(MeHSiO).sub.5 (Me.sub.2 SiO).sub.43 SiMe.sub.2 H; PA1 Me.sub.3 SiO(MeHSiO).sub.22 (MeC.sub.6 H.sub.5 SiO).sub.28 SiMe.sub.3 PA1 Me.sub.3 SiO(MeHSiO).sub.35 SiMe.sub.3 ; PA1 Me.sub.3 SiO(MeHSiO).sub.30 (Me.sub.2 SiO).sub.970 SiMe.sub.3 ; PA1 Me.sub.2 HSiO(Me.sub.2 SiO).sub.450 SiMe.sub.2 H; PA1 Me.sub.3 SiO(MeHSiO).sub.24 (CF.sub.3 CH.sub.2 CH.sub.2 MeSiO).sub.74 SiMe.sub.3 ; PA1 (1) from 5 to 12 carbon atoms; PA1 (2) a terminal ethynyl group; and PA1 (3) an ethenyl group in conjugation with said ethynyl group. PA1 component (A) is present from 0.5 to 99.48 parts; PA1 component (B) is present from 0.5 to 99.48 parts; PA1 component (C) is present from 0.000001 to 1.0 parts; PA1 component (D) is present from 0.01 to 10 parts; and PA1 component (E) is present from 0.01 to 10 parts, PA1 component (A) is present from 92 to 98.5 parts; PA1 component (B) is present from 1.4 to 10 parts; PA1 component (C) is present from 0.004 to 0.50 parts; PA1 component (D) is present from 0.05 to 5 parts; PA1 component (E) is present from 0.05 to 5 parts; PA1 (A) a polyorganosiloxane having the general formula EQU R.sub.3.sup.2 SiO(R.sup.1.sub.a Q.sub.b SiO.sub.(4-a-b)/2).sub.x SiR.sub.3.sup.2, PA1 wherein PA1 (B) a polyorganosiloxane containing hydrogen atoms bonded to silicon atoms; PA1 (C) a catalyst; PA1 (D) a conjugated ene-yne, said conjugated ene-yne characterized by having; PA1 (E) A vinylcyclosiloxane having the general formula EQU (R.sup.5 CH.sub.2 .dbd.CHSiO).sub.m PA1 wherein each R.sup.5 is selected from methyl, ethyl, and phenyl groups, and m has an average value of from 3 to 6; and PA1 (F) a filler. PA1 (A) from 0.5 to 99.48 parts of a polyorganosiloxane having the formula EQU R.sub.3.sup.2 SiO(R.sup.1.sub.a Q.sub.b SiO.sub.(4-a-b)/2).sub.x SiR.sub.3.sup.2, PA1 wherein PA1 (B) from 0.5 to 99.48 parts of a polyorganosiloxane having the formula EQU R.sub.3.sup.4 SiO(R.sup.3.sub.c H.sub.d SiO.sub.(4-c-d)/2).sub.y SiR.sub.3.sup.4, PA1 wherein PA1 (C) from 0.000001 to 1.0 parts, based on the weight of metal, of a catalyst; PA1 (D) from 0.1 to 10 parts of an inhibitor, said inhibitor being a hydrocarbon containing: PA1 (E) from 0.01 to 10 parts of a vinylcyclosiloxane having the general formula EQU (R.sup.5 CH.sub.2 .dbd.CHSiO).sub.m PA1 wherein each R.sup.5 is selected from methyl, ethyl, and phenyl groups, and m has an average value of from 3 to 6; and PA1 (G) from 0 to 4000 parts of a solvent, all of the above parts being parts by weight based on 100 total parts of Components (A) plus (B) plus (D) plus (E). PA1 (A) from 0.5 to 99.48 parts of a polyorganosiloxane having the formula EQU R.sub.3.sup.2 SiO(R.sup.1.sub.a Q.sub.b SiO.sub.(4-a-b)/2).sub.x SiR.sub.3.sup.2, PA1 wherein PA1 wherein PA1 (C) from 0.000001 to 1.0 parts, based on the weight of metal, of a catalyst; PA1 (D) from 0.01 to 10 parts of an inhibitor, said inhibitor being a hydrocarbon containing; PA1 (E) from 0.01 to 10 parts of a vinylcyclosiloxane having the general formula EQU (R.sup.5 CH.sub.2 .dbd.CHSiO).sub.m PA1 wherein each R.sup.5 is selected from methyl, ethyl, and phenyl groups, and m has an average value of from 3 to 6; and PA1 (F) from 0 to 400 parts of a filler, all of the above parts being parts by weight based on 100 total parts of Components (A) plus (B) plus (D) plus (E).
U.S. Pat. No. 4,340,709, issued July 20, 1982, discloses the use of methylvinylcyclotetrasiloxane, triaklylcyanurates, alkyl maleates, and mixtures of the above three types of compounds as inhibitors.
Copending Application for Patent Ser. No. 478,433, filed Mar. 24, 1983 and entitled "Room Temperature Stable, Heat Activated Organopolysiloxane Compositions" discloses the use of conjugated ene-ynes as inhibitors of the reaction of SiH and SiVi.
Conjugated ene-ynes are hydrocarbons containing a triple bond, i.e. and "yne" bond, and a double bond, i.e. an "ene" bond in conjugation with one another.
U.S. Pat. No. 4,340,710, issued July 20, 1982, discloses the use of ethynylically unsaturated isocyanurates and dialkylacetylenecarboxylates conjointly as inhibitors.
The present invention deals with the use, as the inhibitor, of vinylcyclosiloxanes in combination with one or mor conjugated ene-yne. Suprisingly, the use of this combination results in room temperature inhibition of cure that is 5 or more times as effective as the room temperature inhibition of cure observed for comparable levels of either the ene-yne or the vinylcyclosiloxane independently. In addition, no significant reduction in the rate of cure at elevated temperature has been noted. In some cases, actual acceleration of the elevated temperature cure rate has been observed.